The main purpose of the WCDMA Radio Access Network, see schematic example given in FIG. 1, is to provide a connection between the handset and the core network and to isolate all the radio issues from the core network. The advantage is one core network supporting multiple access technologies.
As is well known, the WCDMA Radio Access Network Comprises Two Types of Nodes:
The Radio Base Station (Node B) handles the radio transmission and reception to/from the handset over the radio interface (Uu). It is controlled from the Radio Network Controller via the Iub interface. One Radio Base Station can handle one or more cells.
The Radio Network Controller (RNC) controls all WCDMA Radio Access Network functions. It connects the WCDMA Radio Access Network to the core network via the Iu interface. There are two distinct roles for the RNC, to serve and to control. The Serving Network controller has overall control of the handset that is connected to WCDMA Radio Access Network. It controls the connection on the Iu interface for the handset and it terminates several protocols in the contact between the handset and the WCDMA Radio Access Network. The Controlling RNC has the overall control of a particular set of cells, and their associated base stations.
When a handset requires resources in a cell that are not controlled by its Serving RNC, the Serving RNC must ask the Controlling RNC for those resources. This request is made via the Iur interface, which connects the RNC with each other. In this case, the Controlling RNC is also said to be a Drift RNC for this particular handset. This kind of operation is primarily needed to be able to provide soft handover throughout the network.
The main service offered by WCDMA RAN is providing the Radio Access Bearer (RAB). To establish a call connection between the handset and the base station a RAB is needed. The characteristics of the Radio Access Bearers are different depending on what kind of service/information is to be transported.
The RAB carries the subscriber data between the handset and the core network. It is composed of one Radio Bearer between the handset and the Serving RNC, and one lu bearer between the Serving RNC and the core network.
The 3GPP standardisation body has defined four different quality classes of Radio Access Bearers:                Conversational (used for e.g. voice telephony)        low delay, strict ordering        Streaming (used for e.g. watching a video clip)        moderate delay, strict ordering        Interactive (used for e.g. web surfing)        moderate delay        Background (used for e.g. file transfer)        no delay requirement        
Both the Conversational and Streaming RABs require a certain reservation of resources in the network, and are primarily meant for real-time services. The latter RAB types differ mainly in that the Streaming RAB tolerates a higher delay as long as the delay variation is kept low, appropriate for one-way real-time services.
The Interactive and Background RABs are also called ‘best effort’, i.e. no resources are reserved and the throughput depends on the load in the cell. The only difference between the latter RAB's is that the Interactive RAB provides a priority mechanism.
The RAB is characterized by certain Quality of Service (QoS) parameters, such as bit rate and delay.
The core network will select a RAB with appropriate QoS based on the service request from the subscriber, and ask the RNC to provide such a RAB.
Transport in WCDMA Radio Access Network
The WCDMA Radio Access Network nodes communicate with each other over a trans-port network. The 3GPP specifications provide a very clear split between radio related (WCDMA) functionality and the transport technology, meaning that there is no particular bias to any technology. The transport network may be based on ATM (Asynchronous Transfer Mode) or IP (Internet Protocol).
Transport of packet data units (PDU) between a user entity and a packet data provider network is achieved by means of the GTP (GPRS (General Packet Radio System) Tunnelling Protocol) protocol. The tunnelling protocol utilises encapsulation of Internet packets in GTP packets.
The tunnelling is setup via so-called Packet Data Protocol (PDP) contexts, which exist in the user entities, the SGSN (Serving GPRS Support Node) and the GGSN (Gateway GPRS Support Node). Moreover, the service characteristics of the transmission of PDU are controlled according to the established PDP context. In order to transmit or receive data the user entity must be attached, inferring that a “radio connection” is established between the user entity and the radio base station and a PDP context is activated.
The PDP context comprises                type of the PDP Network (IP or PPP)        address of terminal (IP or PPP)        IP address of SGSN        NSAPI (the logical identifier of the PDP context)        APN: Logical name of the external network (www.internet.com)        Qos        
In document 3GPPTS23.060 V6.9.0, the procedure for PDP-context activation, -modification, -deactivation and -preservation functions are explained.
In FIGS. 2 and 3, the procedure for one known RAB assignment is shown. This procedure corresponds to the PDP Context Activation Procedure for Iu mode, confer, FIG. 64, 3GPP TS 23.060 V6.9.0 (2005-06).
According to the above document, an activate PDP context request is transmitted to the SGSN [0088], corresponding to step 4b in FIG. 3. Subsequently, the GGSN sends a “create PDP context request” to the SGSN carrying a signalling QoS indicator [0090], corresponding to step 4b. Thereafter, the SGSN, sends a RAP assignment request (RANAP) message to the RNC in the UTRAN with the signalling QoS indicator [0091]. Subsequently, the usual steps shown in FIG. 3 are performed.
Thereafter, the SGSN performs the known RAB setup procedure 5.
On the other hand, if the GGSN sends a negative response, the SGSN sends an Activate PDP Context Reject message 9′ to the mobile station.
The GGSN responds by sending a Create PDP Context Response to the SGSN, step 4′.
Dependent on the outcome of the RAB setup procedure, the SGSN sends an Activate PEW Context Accept message, 9, if the RAB setup was successful or an “Activate POP Context Reject message 9′ if the RAB set-up failed. The RAB set up could fail for various reasons such as insufficient link conditions.
Those mobile stations for which the PDP Context activation attempt failed will have to try again to activate the PDP Context at a later stage. This might require manual interaction from the user.
Prior art document US2002/0114305 shows a signalling bearer quality of service profile being pre-established and configured in various nodes in a GPRS/UMTS network.
According to the above document, an activate PDP context request is transmitted to the SGSN [0088], corresponding to step 4b in FIG. 3. Subsequently, the GGSN sends a “create PDP context request” to the SGSN carrying a signalling QoS indicator [0090], corresponding to step 4b. Thereafter, the SGSN, sends a RAP assignment request (RANAP) message to the RNC in the UTRAN with the signalling QoS indicator [0091]. Subsequently the usual steps shown in FIG. 3 is performed. This document forms the preamble of claim 1.
In the above document no evaluation is performed as to RAB set-up criteria being positive or negative, after the SGSN receiving a positive PDP context response from the GGSN, leading to a subsequent omission of a RAB assignment, as in the first embodiment of the present invention.
Prior art document US2002/0036983 shows a mobile station initiated PDP context activation procedure in FIG. 15. After a RAB assignment incomplete message 7 is received by the SGSN, the SGSN responds by issuing a create PDP context request 9 including negotiated QoS to the GGSN. The GGSN issues a Create PDP context response message 10 which is relayed back to the mobile station. Both the SGSN and the GGSN can modify the requested QoS profile. There are several local admission controls taking place in the procedure. However, since bandwidth associated with radio is the most expensive resource, the UTRAN is consulted in determining whether radio resources are available or not during PDP context activation or modification. Thus, admission control in UMTS is performed in a radio centric manner.
It is understood that if the RAB assignment complete 7 is not received by the SGSN, the Activate PDP context accept 11 is not issued to the mobile station.